The present invention relates generally to fuel injectors and, in particular, to a flow master for testing leak test heads that are used to test fuel injectors.
Fuel injectors typically comprise an electromagnetically actuated needle valve disposed in a fuel volume. The needle valve is reciprocated axially within the fuel volume in response to energization and deenergization of an actuator to selectively open and close a flow path through the fuel injector. Particularly, the valve body or housing defining the fuel volume has an aperture or orifice at one end forming a seat for the end of the needle valve whereby its reciprocating motion enables an intermittent flow of fuel through the orifice. Typically, the fuel emitted from a fuel injector is atomized downstream of the orifice to provide the necessary fuel/air mixture in the combustion chamber of the engine.
Referring now to FIG. 1, there is illustrated a prior art fuel injector, generally designated 10, including a housing assembly 12 mounting a coil assembly 14 and an armature 16 coupled to a needle valve 18. Surrounding the needle valve 18 is a housing 22 defining a fuel volume 24 in communication with a fuel flow passage 20 through the armature 16. At the lower end of housing 22 is a valve seat 26 defining an orifice 28 through which fuel is ejected from the fuel ejector into the engine. The coil 14 and armature 16 cooperate to open and close orifice 28 by periodic axial movement of needle valve 18 within fuel volume 24.
Fuel injectors are pressure tested using a leak test head to ensure that there is not too much leakage. The fuel injector is connected to a leak test head which is then pressurized. The leak test head measures the pressure loss through the fuel injector. If the pressure loss is greater than a predetermined amount, then the fuel injector is rejected as unsatisfactory.
The leak test heads are also tested to ensure that they are accurate. The leak test heads are tested with a flow master.
Previous flow masters were bulky and expensive. The physical size of previous flow masters prevented using them on every leak test head simultaneously. Therefore, the process of testing leak test heads was very time consuming.
It is an object of the present invention to provide an improved method and apparatus for testing leak test heads used to test fuel injectors for leakage.
This and other objects of the invention are achieved by a flow master for testing a leak test head comprising a housing having an upper body portion and a lower body portion, the housing defining a passageway therethrough, the housing further defining an internal volume substantially equal to a fuel volume of a fuel injector to be tested; and a porous metal flow restrictor disposed in the passageway.
Preferably, the flow master further comprises a porous metal sintered filter disposed in the upper body portion of the housing.
Another aspect of the invention is a method of testing a leak test head comprising providing a flow master; measuring a flow rate of the flow master from a known standard; connecting the flow master to the leak test head; pressurizing the leak test head; measuring a flow rate through the flow master using the leak test head; and comparing the flow rate measured by the leak test head to the flow rate measured by the known standard to determine if the leak test head is accurate.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing.